This invention deals with a fuel supply system for a direct injected engine and more particularly to an improved high pressure fuel supply system for a direct injected outboard motor.
The charge forming system for internal combustion engines in many applications are becoming more sophisticated in the interest of obtaining better engine performance, both in terms of power output and also in terms of fuel economy and exhaust emission control. The charge formers used have progressed from carburetors to manifold injection and now direct cylinder injection is being strongly considered.
By injecting the fuel directly into the combustion chamber rather than mixing it with the inducted air in the induction system, it is possible to achieve a condition which is referred to as "stratification." It is generally acknowledged that is necessary to have a stoichiometric mixture in order to initiate combustion. However, if the entire cylinder is charged with a stoichiometric mixture, the overall mixture is richer than required for most running conditions.
With stratification, there is provided a stoichiometric fuel air mixture that is intended to be present at the gap of the spark plug at the time it is fired so as to initiate combustion. The remainder of the cylinder surrounding this stoichiometric patch can be leaner than stoichiometric or can, in fact, comprise pure air. In order to achieve this stratification, direct cylinder injection may be necessary. Even without stratification, however, direct cylinder injection has numerous advantages.
In certain engine applications, the utilization of direct cylinder injection presents some design difficulties. The application of fuel injection and direct cylinder injection to outboard motors is an example of such problem areas and applications. This is primarily due to the compact nature of an outboard motor.
With a direct cylinder injection system and in connection with outboard motors because of their compact nature, it is generally required to have a low pressure fuel pump, a high pressure fuel pump and a vapor separator for ensuring that vapor is not delivered to the fuel injectors. The vapor separator is particularly necessary with outboard motor application because of the small space in which the engine is confined and the fact that the engine is generally surrounded by a closely fitting protective cowling. Fuel vapor problems are thus particularly prevalent with outboard motor applications.
With injection systems for outboard motors, it has been the practice to position the high pressure pump directly in the vapor separator. This can save space but does necessitate generally the use of an electrically operated fuel pump. Electric fuel pumps, however, do not generate sufficient pressure for direct cylinder injection in most instances. Thus, in order to enjoy the full benefits of direct cylinder fuel injection, it is necessary to use a higher pressure pump. Normally, positive displacement pumps are employed for this purpose.
When a positive displacement pump is employed, it must be driven off of the engine if sufficiently high pressures as required for direct cylinder injection are to be obtained. This presents problems in layout and positioning of the fuel pump in outboard motors.
This problem is particularly aggravated by the fact that in an outboard motor the engine is mounted so that its output or crankshaft rotates about a vertically extending axis. As is well known, most engine applications position the engine so that the output shaft rotates about a horizontally extending axis.
With outboard motors, on the other hand, the vertical positioning of the engine output shaft is desirable to facilitate and simplify the connection to the driveshaft which drives a propulsion device in the lower unit of the outboard motor. This gives rise to problems and where the high pressure fuel pump is located and how it is driven.
Another problem in connection with outboard motors is that the total sales volume is quite small compared to applications such as automotive applications. Thus, the outboard motor industry has been somewhat slow to make changes following the automotive industry due to the tremendous tooling expenses involved and the fact that long production runs are required to recoup tooling change costs.
Therefore, there is some advantage if automotive components such as high pressure fuel pumps for direct injection system can be employed with outboard motors. However, the vertical positioning of the engine crankshaft means that the automotive fuel pumps cannot be operated in their normal manner as applied to motor vehicles.
That is, in a motor vehicle, the crankshaft rotates about a horizontally extending axis and the plungers of the high pressure pump also reciprocate along horizontal axes. It is not always possible to mount the pump in the outboard motor so that its plungers will reciprocate about a vertical axis. In addition, if the pump is reoriented, certain other problems may arise. For example, reorientation may affect the operation of check valves, particularly if they are gravity biased. Also air purging of the pump can be adversely affected.
It is, therefore, a principal object of this invention to provide an improved drive arrangement wherein plunger type pumps may be driven from the crankshaft of a vertically disposed application for utilization in outboard motors.
It is a further object of this invention to provide an improved drive mechanism for driving a plunger type pump from the vertical output shaft of an outboard motor engine.
Belt drives for driving accessories are quite popular in outboard motors as well as in other applications. Belt drives offer the advantages of quiet operation and also the drive belt can be positioned externally of the engine and thus, air cooled. This also permits the use of a more compact assembly.
However, a belt drive is only practical, in most applications, for transmitting motion between parallel axis shafts. If a plunger type pump is to be employed, therefore, a transmission must be incorporated for transferring the drive from a vertical shaft to a horizontal shaft in most types of applications. This involves the use of a transmission that contains gearing.
If the transmission is positioned externally of the engine, as may be desirable in many instances, then it is necessary to provide an arrangement wherein the transmission will be lubricated. This also necessitates constructing the transmission in such a way that its lubricant can be serviced.
It is, therefore, a still further object of this invention to provide an improved pump drive mechanism that incorporates a transmission which transmission includes gearing and arrangement for servicing the gearing.
It is a further object of this invention to provide a reciprocating pump driving transmission for use in outboard motors.
In some instances it may be desirable to actually circulate lubricant through the drive mechanism for the pump or through the pump drive. Where this is remotely positioned from the engine crankcase this is difficult.
It, therefore, is a further object of this invention to provide an improved lubricating system for the drive arrangement for a high pressure fuel injection pump.
It is a yet further object of this invention to provide an improved lubricating system for a drive arrangement for a high pressure fuel injection pump that is positioned remotely from the crankcase of the engine that it serves.